Post-Fire Studies: Mammals

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In 2002 and 2003, over 1500 square miles of southern California burned in firestorms unequaled for over a century, the largest fires since accurate records have been kept. Because of the fires’ unprecedented size, their effects on the ecosystem were unknown and unpredictable. Over 738 square miles burned in San Diego County alone, 17.4% of the county’s total area and nearly 25% of the area still covered by natural vegetation. The Cedar fire of October 2003 alone burned 436.4 square miles and was the single most pervasive disaster in San Diego history. The fires killed 17 people, compelled the evacuation of thousands, burned 2454 houses, blanketed the region under dense smoke for a week, and shut the business of the city of San Diego down for two days.

Areas burned in San Diego County in 2002 and 2003

These wildfires also reignited the debate among resource managers, politicians, scientists, and the public about the strategies appropriate for people to live in the fire-prone ecosystems of southern California. This debate among vegetation and fire ecologists began in the early 1980s (Keeley 1982, Minnich 1982, Minnich and Chou 1996, Keeley 2002) but has now sprung to the forefront of the public eye and resource managers’ needs.

Developing fire-management strategies in southern California, particularly in coastal sage scrub and chaparral, is particularly difficult because the area is a biodiversity hotspot and supports a large number of threatened and endangered species. Guidelines for prescribed fires must minimize their effect on a wide array of species while simultaneously helping to prevent fires that might threaten lives and property. Such guidelines can be developed only with detailed information on species’ responses to fire and subsequent patterns of recovery. Yet in spite of the central role of fire in the southern California’s biology, few studies have addressed the responses of any vertebrate to fire, and little is known about how animals recover following fire or what interventions, if any, may be necessary to assist ecological recovery following fire.

Our team has two studies focused on understanding mammals’ responses to fire. One, in chaparral in the Cleveland National Forest, is examining how rodents and other small mammals, carnivores, and bats recover from fire, with a special emphasis on how proximity to unburned habitat and fire severity influence recovery. The other study, in coastal sage scrub in Rancho Jamul Ecological Reserve, addresses rodents’ responses to fire, taking into account the influence of the abundance of exotic plants before and after fire.

Our results will ultimately aid the responsible authorities in designing guidelines for how to prepare for fire. The influence of fire severity on mammals’ recovery can be incorporated into considerations regarding fuel status and fire weather before a fire breaks out. The temporal and spatial patterns of mammal recovery can be used to guide minimum fire intervals as well as maximum fire sizes in plans for controlled fires. The effects of the abundance of exotic plants, which may be enhanced by frequent fire, can be used to guide postfire management interventions to assist recovery. As a whole, the information resulting from these studies will aid planning for fire management with the minimum effect on southern California’s mammals.

Acknowledgements

In 2002, the San Diego Natural History Museum began a series of studies on the effects of fire on the birds and mammals of San Diego County.

These studies were funded by California State Parks, the Joint Fire Science Program, and the U.S. Forest Service.

We are currently synthesizing the results from these studies in ways to inform monitoring and adaptive management techniques and strategies. This project is funded by a grant from the Blasker Environment Grant Program of the San Diego Foundation.